The cell surface has been one of the focal points in the studies on malignancy. General changes in structures of cell surface glycoconjugates as well as the presence of unique glycoconjugates in malignant cell surface have been reported. The long-range objective of this study is to contribute to the structure-function relationships of cancer cell surface glycoproteins and malignancy. The emphasis will be on the high molecular weight cell surface sialoglycoproteins (termed Ca antigen) which are detectable by Cal monoclonal antibody on a wide variety of human malignant cells. The primary objective is to carry out full biochemical characterization of the Ca antigen. Cal monoclonal antibody will be employed as affinity ligand for the isolation of the Ca antigen from human laryngeal carcinoma cells. The 390K and 350K species of the Ca antigen will be purified and their detailed chemical structure elucidated. The carbohydrate and protein composition, oligosaccharide type and location, and subunit structure are some of the aspects which will be studied. The counterpart of Ca antigen from human melanoma cells and the Ca antigen-like glycoproteins present in normal human urine will also be purified. The structural and immunological relationships of these materials and Ca antigen will be established. Polyclonal and monoclonal antibodies to the purified Ca antigen glycoproteins will be produced and used for understanding the above relationship. It is hoped that the information obtained in these studies will help to establish the potential use of Ca antigen as a human tumor marker. This glycoprotein antigen could be of use for the early diagnosis of cancer, for monitoring the course of disease, for localizing tumors, and for directing drugs to the tumor. (1)